Water temperature regulating pool cover

ABSTRACT

A pool cover for temperature regulation of pool water having an upper sheet of flexible material and a lower sheet of flexible material. The sheets are joined together at their side edges and along a plurality of longitudinally seams to form a panel having a plurality of longitudinal seams to provide a plurality of flow channels. A pump attached to an input tube draws in water from the pool, and via an input manifold forces the pumped water through the flow channels in the panel, and out the ends of the flow channels back into the pool. Pool water pumped through the flow channels picks up heat from incident solar radiation and the ambient air temperature, or gives off heat to the ambient environment, depending on the temperature of the air, the amount of incident radiation, and the temperature control settings provided by the user.

RELATED APPLICATIONS

The present application is based on and claims priority to provisionalapplication Ser. No. 63/283,463, filed Nov. 28, 2021 by Richard MarkHirsch and Keith Eric Forsman, and bearing the title “Water temperatureregulating pool cover.”

FIELD OF THE INVENTION

The present invention is related to temperature control systems,temperature regulation systems, heat collectors, and heat insulators.The present invention is also related to swimming pool equipment, andmore particularly to swimming pool covers and particularly swimming poolcovers for control and/or regulation of pool water temperature.

BACKGROUND OF THE INVENTION

Swimming is a much enjoyed recreation and a useful exercise. However,there is a rather narrow range of water temperatures that are considereddesirable, and water temperatures which are too warm, especially in awarm climate, or too cold, especially in a cold climate, areproblematic. Therefore, there is much call for an economical,easy-to-use pool cover which will effectively heat pool water usingsolar energy, thereby reducing heating costs and extending the range ofseasons during which a pool can be used. This is particularly an issuein the more Northern and Southern latitudes where temperatures dropconsiderably in the fall and spring relative to the summer. Furthermore,in hotter regions, radiant energy from the sun may warm a pool to anundesirably high temperature, so there is also call for a system forcooling pool water. Water has a relatively large heat capacity and poolscontain large quantities of water, so it is particularly important thatthe means for temperature regulation for pools be efficient andeconomical. This may become even more of an issue as climate changesresult in unusual weather patterns.

Typical pool covers float on the water's surface when laid out, and aretypically retracted by spooling onto an axle. Some pool covers aredesigned to be laid out and retracted (i.e., “positioned”) manually,while others are positioned using an electric motor attached to cablesthat run along the sides of the pool. Traditional swimming pool coversdo provide some heat insulation. Swimming pool covers are also usefulfor prevent evaporation of pool water and pool chemicals, and are usedfor safety purposes to prevent people, particularly unattended children,from falling into a pool.

Consider a typical spring or fall day, for instance, in Austin, Tex.,where the solar radiation at ground level is about 650 W/m², and a poolowner is hoping to go swimming even through it is not summer yet orsummer has passed, respectively. Since the heat capacity of water isabout 4.2 J/g° C., and considering a pool with an average depth of 2.5meters, if all the solar energy incident on the pool could be harnessedthe pool could be heated by almost 4° C. per hour. This is more thanenough heating for a pool owner to be able to utilize the pool for sayan hour a day well into the off-seasons. (In fact, so much excess energycan be harvested that according to an alternate embodiment the system ofthe present invention incorporates a storage battery to store the excessin collected energy.)

The pool cover of the present invention has a flexible panel which hasan upper sheet and a lower sheet, both of a flexible plastic material.The upper and lower sheets having essentially the same shape and sizeand are joined at their side edges to provide a waterproof seal.According to the present invention the upper sheet and the lower sheetare also joined along longitudinally-oriented seams to provide a seriesof flow channels. A pump connected to an input manifold at the front endof the panel forces water into the front end of the flow channels, andan output manifold at the rear end of the panel allows the output ofwater from the rear end of the flow channels. The system activelyregulates the pool temperature to keep it within a specified range bymonitoring the water temperature and/or the air temperature and/or thelevel of incident solar energy, and controlling pumping of the waterthrough the flow channels to absorb heat from the ambient environment orrelease heat to the ambient environment.

Based on the above description of the background of the invention andthe detailed description below, following are objects of the presentinvention.

It is an object of the present invention to provide a pool cover whichis easy to use.

It is an object of the present invention to provide a pool cover whichhas a small volume when spooled onto an axle.

It is an object of the present invention to provide a pool cover whichcan efficiently harvest solar energy to warm pool water.

It is another object of the present invention to provide a pool coverwhich can efficiently cool pool water by transfer of heat energy in thewater into the ambient environment, particularly at night when airtemperature is lowest.

It is an object of the present invention to actively regulate thetemperature of pool water through the generation of fluid flows based onone or more sensor measurements, such sensors monitoring a watertemperature or multiple water temperatures, and/or ambient airtemperature, and/or incident solar radiation.

It is another object of the present invention to provide a pool coverwith water flow channels which produces efficient transfer of energybetween the pool water and the ambient environment.

It is another object of the present invention to provide a pool coverwith an input manifold to water flow channels in the cover which evenlydistributes water flow between the flow channels.

Additional objects and advantages of the invention will be set forth inthe description which follows, and will be obvious from the descriptionor may be learned by practice of the invention. The objects andadvantages of the invention may be realized and obtained by means of theinstrumentalities and combinations particularly pointed out in theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a top plan view of the pool cover of the present invention ona pool.

FIG. 2A is a cross sectional side view of a pool cover according to thepresent invention on the pool with an uptake tube which extends to nearthe bottom of the deep end of the pool.

FIG. 2B is a cross sectional side view of a pool cover according to thepresent invention on the pool with an uptake tube which extends to nearthe top surface of the pool.

FIG. 3 is an enlarged sectional end view showing the graduated aperturediameters of the input manifold utilized to achieve uniform flow ratesacross the flow channels.

FIG. 4 is a schematic of the electrical control system of the pool coverof the present invention.

FIG. 5 shows an interface for control of the settings of the temperatureregulating pool cover of the present invention.

FIG. 6 is a flowchart showing the decision and control processes of theactive temperature regulating pool cover of the present invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to the lexicography of the present invention, a “pool” isconsidered to be any body of water or other liquid exposed to theambient environment. That being said, the use of particular interest andthat addressed most specifically herein is the temperature regulation ofswimming pools.

FIG. 1 shows a top plan view of the pool cover (100) of the presentinvention on a pool (90). FIG. 2A shows a cross sectional side view ofthe pool cover (100) on the pool (99) according to aheating-functionality embodiment where a water uptake tube (210) extendsto near the bottom of the deep region (92) of the pool (90). FIG. 3shows a cut-away end view of the first three end-most flow channels(120.1), (120.2) and (120.3) of the pool cover (100).

The pool cover (100) of the present invention has a flexible panel (110)which can substantially cover the surface of the water (80) in the pool(90), as is shown in FIGS. 2A and 2B. The panel (110) has a flexibleupper sheet (111 a) and a flexible lower sheet (111 b), as is shown inFIG. 3 . The upper and lower sheets (111 a) and (111 b) are joined atside edges (109.1) and (109.2), shown in FIG. 1 , and are joined alongparallel, longitudinal-running seams (130.1), (130.2), (130.3), . . . toform a multiplicity of flow channels (120.1), (120.2), (120.3) . . . .(The seams will be referred to generically or collectively withreference numeral “130” and the flow channels will be referred togenerically or collectively with reference numeral “120.”). The seams(130) and the seams at the sides of the sheets (111) are water-proof.Preferably, the sheets (111) are made of a uv-resistant,puncture-resistant 0.015 cm or 0.020 cm thick vinyl, and may possiblyinclude reenforcement. It is advantageous to use materials which are asthin as possible for the upper and lower sheets (111 a) and (111 b)since the pool cover (100) needs to be retracted when the pool is inuse, and that is typically accomplished by rolling the panel (110) uparound a spool (not shown). Furthermore, it is advantageous to use asthin a material as possible for the upper and lower sheets (111 a) and(111 b) since flow of heat through the sheets (111 a) and (111 b) fromtop to bottom is inversely related to their thickness.

According to a preferred embodiment of the heating-functionalityembodiment, the upper sheet (111 a) is opaque and of a dark color,preferably a dark blue, to maximize absorption of incident solarradiation (60) and minimize reflection of incident radiation (60).Furthermore, the top surface of the upper sheet (111 a) may be coatedwith an absorption-enhancing or anti-reflective coating in order tominimize reflected energy. As is well known in the art, anti-reflectivecoatings utilize destructive interference between energy reflected atthe top and bottom surfaces of the coating to minimize reflected energy.The anti-reflective coating may be a powder or laminated film. Accordingto the present invention, the thickness of the coating is thereforeselected to correspond to the half wavelength of a frequency of lightcentral to the range of frequencies providing the most incident energy.In particular, the coating has a thickness to create destructiveinterference for incident radiation with a wavelength of roughly 500 nm.(Wavelengths in the coating material will differ from wavelengths in avacuum or the ambient environment because of the index of refraction ofthe coating material.) Furthermore, to maximize incident energyabsorption, particles may be added to the material used to form thesheet (111 a) or (111 b) in the form of a filing, mixture, or modifiedcompound, as well as threads, filaments, etc. Possibleabsorption-enhancing or anti-reflective materials include, but are notlimited to, carbon black, aluminum, copper oxides and other metaloxides. Furthermore, such materials might also be used to increasethermal conductivity and affect heat capacity.

According to a preferred embodiment of the present invention, thematerial used to form the upper sheet (111 a) (and possibly also thelower sheet (111 b)) incorporates graphene because of a synergy of threeproperties of graphene which make it particularly useful for purposesand objects of the present invention. Graphene is an allotrope of carbonconsisting of a single layer/plane of atoms having a two-dimensionalhoneycomb lattice arrangement. The material has an extremely hightensile strength, extremely high thermal conductivity in the plane ofthe atoms, and absorbs incident energy over a broad range ofwavelengths. A panel of graphene is about 100 times stronger than wouldbe a panel of steel of the same thickness, and is the strongest materialknown to man. Incorporating graphene in the material of the sheets (111a) and (111 b) allows the thickness of the sheets (111 a) and (111 b) tobe minimized so the panel (110), when wrapped around the spool, takes upa minimum of volume. Furthermore, graphene has thermal conductivity thatmay reach as high as 5300 W m⁻¹ K⁻¹. Although this upper limit tothermal conductivity may not be reached in practice without addingconsiderable expense to the manufacturing cost, realistic thermalconductivity values as high as 500 W m⁻¹ K⁻¹ to 600 W m⁻¹ K⁻¹ make thematerial useful for the present invention. Furthermore, the surprisinglyhigh opacity of graphene, particularly in the visible and infraredfrequency ranges, makes it an efficient absorber of incident solarradiation (60).

According to one preferred embodiment of the present invention, thelower sheet (111 b) functions to provide insulation between the water(80) below the cover panel (110) and in the flow channels (120), whilethe upper sheet (111 a) allows for heat transfer between the water (80)which flows through the channels (120) and the ambient air (70). Ifgraphene is incorporated into the upper sheet (111 a) in the form ofrelatively large planes of the material, the planes should extend tosome extent in the direction from the upper surface of the upper sheet(111 a) to the lower surface of the upper sheet (111 a). If graphene isincorporated into the upper sheet (111 a) in the form of a relativelyfine powder, then the randomness of the orientations of the grains ofthe powder will insure that a portion of the grains will have anorientation so as to provide thermal conductivity between the upper andlower surfaces of the upper sheet (111 a). If graphene is incorporatedinto the lower sheet (111 b) in the form of relatively large planes ofthe material, then the planes should extend substantially parallel tothe upper and lower surfaces of the lower sheet (111 b) so the lowersheet (111 b) will have a low thermal conductivity between its top andbottom surfaces.

According to one preferred embodiment of the present invention, theupper sheet (111 a) is transparent and the lower sheet (111 b) is opaqueand of a dark color, preferably a dark blue, in order to absorb a largeportion of the incident radiation (60). The advantage of this embodimentis that the heat energy exiting the heat-absorbing sheet (in this casethe lower sheet (111 b)) is useful when exiting in both the upwards anddownwards directions. Heat exiting upwards heats the water (90) flowingthrough the flow channels (120), and heat exiting downwards heats thewater (90) just under the pool cover. The top surface of the lower sheet(111 b) may be coated with an absorption-enhancing or anti-reflectivecoating in order to minimize reflected energy having a wavelengthcentral to the range of frequencies providing the most incident energy,i.e., roughly 500 nm.

Because the water (80) in the pool (90) is coldest in the deep region,and because the energy transfer is proportional to the temperaturedifferential and therefore most efficient when there is a largetemperature differential, the pumping system (200) pumps water up fromthe deep region (92) of the pool (90), the pumping system (200) has aflexible uptake tube (210) which has a length comparable to or greaterthan the depth of the deep region (92) of the pool (90) in order to pumpwater (80) from the deep region (92). The upper end (211) of the uptaketube (210) flow connects to an input manifold (220), and the inputmanifold (220) flow connects to the input edge (109.3) of the panel(110). (According to the lexicography of the present specification, afirst component is said to “flow connect” to a second component whenwater channeled through the first component is forced into the secondcomponent with little to no leakage elsewhere.) Pool water (80) pumpedthrough the flow channels (120) picks up heat from the panel (110) as ittravels the length of the flow channels (120) before emptying into thepool (90) at the end (109.4) of the panel (110) opposite the inputmanifold (220). According to the preferred embodiment of the presentinvention, the pump (230) is a portable low-flow fractional horsepowerwater pump and is powered by a solar panel (240) mounted on the top ofthe input manifold (220). (Alternatively, the pump (230) is powered by achord connected to a standard wall socket electrical outlet or by abattery.)

The input manifold (220) has a series of input manifold apertures(225.1), (225.2), (225.3) . . . with inter-aperture spacing equal to thewidths of the flow channels (120). (The input manifold apertures will bereferred to generically or collectively with reference numeral “225.”)The pump (230) along the uptake tube (210) draws water in at the lowerend (211) of the uptake tube (210) and forces it out the upper end (212)of the uptake tube (210), into the input manifold (220), through themanifold apertures (225), and into and along the flow channels (120).Water pressure decreases along the length of the input manifold (220) inthe rightwards direction so, as can be seen by the exaggerateddifferences in the diameters of the input manifold apertures (225) inFIG. 3 , the diameters of the input manifold apertures (225) increasefrom left to right. This insures that the water flow is even distributedacross the flow channels (120), i.e., roughly an equal amount of waterflows through each flow channel (120), in order to maximize heattransfer from solar radiation incident on panel (110) to the water (80)in the pool (90).

In one preferred embodiment of the present invention the pool cover(100) has an on-off switch (301) and the user simply turns it on when itis desired that the temperature of the water (80) be increased and theambient conditions (i.e., air temperature, water temperature, andincident radiation) make heating of the water (80) possible. Accordingto a more sophisticated embodiment, the system further includes one ormore temperature sensors and a processor. A schematic (400) of theelectrical control system for the active pool water temperature controlsystem according to a more sophisticated embodiment is shown in FIG. 4 .(The electrical connection wirings between the various electricalcomponents are depicted in FIG. 4 but for the sake of clarity ofdepiction the wirings are not depicted in the other figures.) Accordingto the present invention, the control system (400) may have a deep watertemperature sensor (310) mounted on the uptake tube (210) near itsbottom end (211), a surface water temperature sensor (320) mounted onthe uptake tube (210) near its upper end (212), an air temperaturesensor (423) mounted on the top side of the input manifold (220), alight meter (424) also mounted on the top side of the input manifold(220), and a processor (410) mounted on the input manifold (220). In onepreferred embodiment, the control system (400) further includes a solarpanel (240) to convert incident solar radiation (60) into electricalenergy to power the processor (410) and the pump (230). (It is assumedthat the on/off switch (301), deep water temperature sensor (310),surface water temperature sensor (320), air temperature sensor (423),and light meter (424) are passive components, although these mayalternatively be powered components.)

The control system (400) utilizes temperature monitoring via one or moresensors (310), (320), (423) and (424) to control the pumping performedby the pump (230). (It should be noted that the pool cover (100) of thepresent invention which is utilized, as described above to absorbdaytime solar energy (60) to heat the pool water (80), may also be usedto transfer the heat energy of pool water (80) to the ambientenvironment (70), particularly at night.) According to a preferredembodiment of the present invention, programming and control of theprocessor (410) is implemented via an app on a mobile phone whichcommunicates with the processor (410) via a blue tooth interface. Theimplementation of mobile phone apps is well-known in the art of mobilephone application programming. According to the preferred embodiment, auser may utilize the app to specify variables such as a targettemperature or a target temperature range for the pool water (80),and/or may schedule pumping based on a clock (412) incorporated in theprocessor (410), and/or may access weather data, such as predicted airtemperature or cloudiness as a function of time, via an Internetconnection (not shown in FIG. 4 ) to schedule the functioning of thesystem (100) for optimum performance and efficient energy usage.

According to an embodiment of the present invention which functionspredominantly to lower the water temperature, the temperature of thewater (80) in the pool (90) is lowered by reducing the amount of solarenergy (60) reaching the water (80), and/or providing insulation betweenthe water (90) and the ambient air (70), and/or facilitating heattransfer to the ambient air (70) when the air (70) is cooler. Accordingto this cooling-functionality embodiment, the upper sheet (111a) ishighly reflective of incident solar radiation (60). Such reflectivitymay be achieved by the use of films and coatings such as is well knownin the art, such as the art of films and coatings commonly applied tothe windows of buildings to reflect solar energy, or the top surface ofthe upper sheet (111 a) may be “metallized”, such as with aluminum,silver, titanium, metal oxides, etc.

As with the heating-functionality embodiment described above, the poolcover (100) has a flexible panel (110) which can substantially cover thesurface of the water (80) in the pool (90), as is shown in FIG. 1 . Thepanel (110) has a flexible upper sheet (111 a) and a flexible lowersheet (111 b). Preferably, the sheets (111) are made of a uv-resistant,puncture-resistant 0.015 cm or 0.020 cm thick vinyl. It is generallyadvantageous to use materials which are as thin as possible for theupper and lower sheets (111 a) and (111 b) since the pool cover (100)needs to be removed from covering the water (80) when the pool is inuse, and that is typically accomplished by rolling the panel (110) uparound a spool (not shown). The upper and lower sheets (111 a) and (111b) are joined at side edges (109.1) and (109.2) and are joined alongparallel, longitudinal-running seams (130.1), (130.2), (130.3) . . . .to form a multiplicity of flow channels (120.1), (120.2), (120.3) . . .. (The seams will be referred to generically or collectively withreference numeral “130” and the flow channels will be referred togenerically or collectively with reference numeral “120.”) The seams(130) and the seams at the sides of the sheets (111) are water-proof.

According to a preferred embodiment of the present invention, the lowersheet (111 b) functions to provide insulation between the water (80) andthe air (70), while the upper sheet (111 a) allows for heat transferbetween the water (80) which flows through the channels (120) and theambient air (70). According to a preferred embodiment, the material usedto form the upper sheet (111 a) incorporates graphene in the form of afiling, mixture, or modified compound, or in the form of graphenethreads, filaments, etc. because of a synergy of properties of thematerial which make it particularly useful. Because of graphene'sextremely high tensile strength, incorporating it in the material of theupper sheet (111 a) allows the thickness of the sheet (111 a) to beminimized, which is advantageous since the rate of conduction of heatthrough the upper sheet (111 a) is inversely related to its thickness.And the high thermal conductivity of graphene further facilitates thetransfer of heat from the water (80) which flows through the flowchannels (120) to the ambient air (70).

If graphene is incorporated into the upper sheet (111 a) in the form ofrelatively large planes of the material, the planes should extend tosome extent in the direction from the upper surface of the upper sheet(111 a) to the lower surface of the upper sheet (111 a). If graphene isincorporated into the upper sheet (111 a) in the form of a relativelyfine powder, then the randomness of the orientations of the grains ofthe powder will insure that a portion of the grains will have anorientation so as to provide thermal conductivity between the upper andlower surfaces of the upper sheet (111 a). If graphene is incorporatedinto the lower sheet (111 b) then the planes of the graphene atoms mustextend substantially parallel to the upper and lower surfaces of thelower sheet (111 b) to provide a low thermal conductivity from the topsurface to the bottom surface of the lower sheet (111 b).

In an alternate embodiment graphene is not utilized to reduce thethickness of the sheets (111 a) and (111 b). To allow the pool cover(100) of the present invention to be stored at the edge of the pool (90)in the space generally provided for a traditional pool cover, the sizeof the pool cover (100) when rolled up is minimized by using a mechanismto squeeze water and air out from the flow channels (120) and frombetween the space between the outside surfaces of the sheets (111 a) and(111 b) when the pool cover (100) is in its rolled-up state. Themechanism to accomplish this may provide additional longitudinal and/ortransverse tensioning during the rolling-up process. Furthermore, thelongitudinal seams (130) may run askew from the longitudinal axis of thepool cover by a small angle ß so that when rolled up the stitchings ofthe seams (130) do not overlap from layer to layer in order to minimizethe diameter of the rolled-up pool cover (100).

A pumping system (200′) has a short flexible uptake tube (210′) so it(200′) pumps water from near the top surface (94) of the pool (90),where the water (80) is warmest, through the flow channels (120). Theupper end (212) of the uptake tube (210′) flow connects to the inputmanifold (220), and the input manifold (220) flow connects to the inputedge (109.3) of the panel (110). As described above, the input manifold(220) has a series of manifold apertures (225.1), (225.2), (225.3) . . .with inter-aperture spacing equal to the widths of the flow channels(120). A pump (230) draws water in at the lower end (211′) of the uptaketube (210′) and forces it out the upper end (212) of the uptake tube(210), into the input manifold (220), through the manifold apertures(225), and into and along the flow channels (120). As described above,the diameters of the manifold apertures (225) increase from left toright to insure that roughly an equal amount of water flows through eachflow channel (120) in order to maximize heat transfer from the panel(110) into the ambient environment (70). The pump (230) is preferably aportable low-flow fractional horsepower water pump and is powered by asolar panel (240) mounted on the top of the input manifold (220).(Alternatively, the pump (230) is powered by a chord connected to astandard wall socket electrical outlet or by a battery.)

In one preferred embodiment of the present invention the pool cover(100) has an on-off switch (301) and the user simply turns it on when itis desired that the temperature of the water (80) be reduced. Butaccording to a more sophisticated embodiment, the system utilizes theelectrical control system (400) of FIG. 4 except that there will not bedeep water temperature sensor (310). The system (400) utilizestemperature monitoring via one or more of the sensors (320), (423) and(424) to control the pumping performed by the pump (230).

As described above for the heating-functionality embodiment, accordingto a preferred embodiment of this cooling-functionality embodimentprogramming and control of the control processor (410) is implementedvia an app on a mobile phone which communicates with the controlprocessor (410) via a blue tooth interface. A user may utilize the appto specify variables such as a target temperature or a targettemperature range for the pool water (80), and/or may schedule pumpingbased on a clock (412) incorporated in the processor (410), and/or mayaccess weather data, such as predicted air temperature or cloudiness asa function of time, via an Internet connection (not shown in FIG. 4 ) toschedule the functioning of the system (100) for optimum performance andefficient energy usage.

A control interface (500) for the pool cover temperature regulatingsystem of the present invention is shown in FIG. 5 . The interface hasan on-off switch (501), a time slots settings section (505), and atarget temperature section (550). The master on-off switch (501) can beswitched from an on setting when the control button (502) is to the left(as is depicted in FIG. 5 ) to an off setting by sliding the controlbutton (502) rightwards. Similarly, when the system is off and thecontrol button (502) is rightwards, the control button (502) can beswiped leftwards to turn the system on. The time slots settings section(505) has three time control slots (510), (520) and (530). Each timecontrol slot (510), (520) and (530) allows for control of the beginningtime and ending time of temperature regulation by the system, has anauto-retract switch (516), (526) and (536) to control whether the coveris retracted at the end of a time slot, and has an on-off button (511),(521) and (531) to switch between making that time control slot (510),(520) and (530) active and inactive. Each time slot (510), (520) and(530) has a start time control (512), (522), and (532) and an end timecontrol (513), (523) and (533). The start and end times of each timeslot (510), (520) and (530) can be set by the user by scrolling up anddown on the hour and/or minutes and or AM/PM selection (similar to how,for instance, alarm times are set on an iPhone made by Apple Computersof Cupertino, Calif.). Although the interface (500) is depicted ashaving three time slot settings sections (510), (520) and (530),according to the present invention the interface (500) may have more orless than three slot settings sections. Below the time period controlsection (505) is a temperature control section (550) which allows atarget temperature and a target temperature range to be set. The targettemperature is set by scrolling the temperature value displayed in thetarget temperature window (551) upwards or downwards, and the targettemperature range is set by scrolling the temperature range valuedisplayed in the target temperature range window (552) upwards ordownwards. In FIG. 5 , the target temperature is 83° F. and the range is+/−1.3° F. so if the ambient environment can provide sufficient heatand/or cool while the system is active the temperature of the pool (90)stays between 81.7° F. and 84.3° F.

The advantage of having multiple time control slots is illustrated, forinstance, by an exemplary situation where the system is used for thepool of a family where, on most weekdays, the children have from shortlyafter they get home from school at 3:30 pm to shortly before dinner at5:30 pm to use the pool. The start time in the start time window (512)of the first time control section (510) is set to 8:00 am, which is whenthe sun in this exemplary situation is high enough that solar radiationcan begin to efficiently provide heating. Since the auto-retract switch(526) of the 5:30 pm to 7:30 pm time period (520) (which was the lasttime slot of the day chronologically) is in the off position, at 8:00 amthe pool cover (100) remains extended after having been in the extendedposition overnight, possibly for the purpose of preventing overnightheat loss. At 8:00 am, the beginning of the first time slot (510) of theday, the system activates the pump (230) and heating of the pool (90)begins. The time in the end time window (513) of the first time slot(510) is set to 3:30 pm, which is when the children have gotten homefrom school and may use the pool (90). Since no other active time periodabuts or overlaps this time, pumping of the pump (230) ceases and thepool cover (100) retracts since the control button (517) of theauto-retract switch (516) of the first time slot (510) is in the onposition. (It should be noted that the control button (535) of theon-off switch (535) of the third time slot (530) is in the off position,so there is no temperature control for the period from 3:30 pm to 5:30pm.) The system having been in operation from 8:00 am to 3:30 pm, thetemperature of the pool (90) is hopefully within the target range oftemperature 83° F. +/−1.3° F. and the children enjoy a comfortable watertemperature during their swim. In this exemplary situation the childrenare required to get out of the pool (90) shortly before their dinnertime at 5:30 pm, and at 5:30 pm the second time period begins since thetime in the start time window (522) of the second time slot (520) is setto 5:30 pm. The system therefore extends the cover (100) over the pool(90) and activates the pump (230), and utilizing the last of thereasonably-strong sunlight of the day the heating of the pool (90)continues. The time in the end time window (523) of the second timeperiod (520) is set to 7:30 pm, which is when solar radiation during thetime of year in this exemplary situation has diminished to an extentthat it is not energetically worthwhile to continue operation of pump(230) of the temperature control system. Therefore, pumping of waterthrough the pool cover (100) ceases at 7:30 pm, and because the controlbutton (527) of the auto-retract switch (526) is in the off position,the pool cover (100) stays extended overnight. This may provide thebenefit of preventing heat loss to the cold ambient air during thenight.

On days when the children have other activities, such as baseball orsoccer games or practices, they will not be home to swim during the timegap between the periods specified in the first and second time slots(510) and (520). And such days a parent may simply swipe the controlbutton (535) of the on-off switch (531) of the third time control period(530) leftwards to activate heating during the gap between the end ofthe first time slot (510) and the beginning of the second time slot(520) when the children would normally be using the pool. Because theend of the first time slot (510) abuts the beginning of the third timeslot (530), the pool cover (100) does not retract, but instead remainsextended and the system continues to utilize solar radiation to heat thepool (90) during the third time slot (530).

A flowchart showing the decision and control process (600) of the systemof the present invention is shown in FIG. 6 . The process (600) begins(601) by first determining (605) whether the control button (502) of theon-off switch (501) is in the on position. If not (606), the process(600) returns (670). If so (607), the pool temperature sensor (310) ismonitored to determine whether the current temperature is within therange specified in the target temperature section (550) of the controlinterface (500). If so (612), the process (600) returns (670). If not(611), it is then determined (615) whether the current time is within aspecified time range of any of the active time slots (510), (520) and(530), i.e., any of the time slots (510), (520) and (530) where thecontrol button (515), (525) and (535) of the on-off switch (511), (521)and (531) is in the on position. If not (616), it is determined (680)whether the pool cover (100) should be retracted. As described above,this will depend on whether the time slot (510), (520), or (530) whichhas a time period which most recently ended had the control button(517), (527) or (537) of its auto-retract switch (516), (526) or (536)in the on position and whether the pool cover (100) had not yet beenretracted. If so (682), the pool cover (100) is retracted (685) and theprocess (600) returns (670). If not (681), the process (600) simplyreturns (670). If it is determined (615) that the current time is (617)within a time range specified by of any of the active time slots (510),(520) and (530), it is then determined (620) whether the pool cover(100) is extended. If not (621), the pool cover (100) is extended andthe process (500) proceeds to step (630). If so (622), the process (500)proceeds directly to step (630). At step (630) it is determined whetherthe pool temperature is less than the bottom of the target temperaturerange specified in the target temperature section (550) of the controlinterface (500). If so (632), then it is determined (650) whether theair temperature as measured by the air temperature sensor (423) and theincident solar radiation as measured by the light meter (424) aresufficiently high to allow pumping of water through the pool cover (100)to heat the pool (90). If so (651), pumping (660) is initiated. If not(652), the process (600) returns (670). If at step (630) it isdetermined that the pool temperature is not (631) less than the bottomof the target temperature range, then it is determined (635) whether thepool temperature is greater than the top of the target temperature rangespecified in the target temperature section (550) of the controlinterface (500). If not (636), then the temperature of the pool (90) iswithin the desired temperature range and the process (600) returns(670). If so (637), then it is determined (640) whether the airtemperature as measured by the air temperature sensor (423) and theincident solar radiation as measured by the light meter (424) are lowenough to allow pumping of water through the pool cover (100) to coolthe pool (90). If so (641), pumping (660) is initiated. If not (642),the process (600) returns (670).

Hence, a water temperature regulating pool cover performing theabove-described objects and providing the above-described advantages istaught. It is to be understood that the foregoing descriptions ofspecific embodiments of the present invention have been presented forpurposes of illustration and description. They are not intended to beexhaustive or to limit the invention to the precise forms disclosed, andit should be understood that many modifications and variations arepossible in light of the above teaching. The embodiments were chosen anddescribed in order to best explain the principles of the invention andits practical application, to thereby enable those skilled in the art tobest utilize the invention and the various elements of the embodiments,alone or in any combination, with various modifications as are suited tothe particular use contemplated. Hence, many other variations arepossible. For example: thin-film photovoltaic solar electric ribbons orpanels attached to the top sheet may be utilized to generate theelectricity for the pump and/or processor; features of theabove-described heating system may be combined with features of theabove-described cooling system, or vice versa; the system may notactively monitor water temperature; the channels may be wider ornarrower than described; the materials of the top and bottom sheets maybe different from what is described; the sheets may have a thicknesssmaller or larger than what is described; the top sheet of the poolcover panel may be clear and the bottom sheet may be a dark color toabsorb incident solar radiation; the pump may be located elsewhere alongthe uptake tube, such as nearer the sheet; water may be input to theinput manifold from both ends rather than a single end; the flowchannels may having differing widths; the panel of the pool cover mayhave more or fewer flow channels that shown and described above; theflow channels may be oriented transversely, rather than longitudinally,i.e., across the width of the pool rather than the length of the pool;the sheets may be thinner or thicker than described; the system mayallow the user to control more or less than three time slots; the systemmay allow for different target temperatures for each time period;extension and retraction of the pool cover may not be controlled by thesystem and, rather, may be performed manually; the system may include acontrol system of more or less sophistication than that described; thecontrol system may select water from a variety of depths based ontemperature variation within the pool; the system may utilize weatherpredictions and/or seasonal information such as local sunrise and sunsettimes; etc. Furthermore, a hybrid embodiment incorporating features ofboth the heating functionality and the cooling functionality arepossible. For instance, there may be a pump at one longitudinal end ofthe panel with an inlet near the upper surface of the water and anotherpump at the other longitudinal end of the panel with an inlet near thebottom of the deep end of the pool. This hybrid embodiment may have someflow channels adapted for heating the pool water and some flow channelsadapted for cooling pool water. Accordingly, it is intended that thescope of the invention be determined not by the embodiments illustratedor the physical analyses motivating the illustrated embodiments, butrather by the appended Claims and their legal equivalents.

What is claimed is:
 1. A pool cover for temperature regulation of poolwater, comprising: a flexible panel having an upper sheet of flexiblematerial having a front edge, a back edge, and side edges, a lower sheetof flexible material having a front edge, a back edge, and side edges,said side edges of said upper sheet and said lower sheet being joined toprovide a waterproof seal, said upper sheet and said lower sheet beingjoined at a plurality of seams to form flow channels between said seams,a cover input manifold, said input manifold being flow connected to saidfront edge of said flexible panel, said input manifold having an inputaperture for each of said flow channels, a pump for pumping waterthrough said input manifold and into said channels to produce water flowfrom front edges of said flow channels to back edges of said flowchannels, and an uptake tube for drawing water from said pool to saidpump, whereby temperature of water flowing through said flow channels isaltered by contact with said upper sheet which is in thermal contactwith an ambient environment.
 2. The pool cover of claim 1 wherein saidflow channels are substantially parallel.
 3. The pool cover of claim 2wherein said flow channels have longitudinal axes substantially alignedwith a longitudinal axis of the pool cover.
 4. The pool cover of claim 1wherein sizes of said apertures provide substantially equal flow througheach of said channels.
 5. The pool cover of claim 1 wherein said uptaketube has sufficient length to extend to a lower region of said pool inorder to draw cooler temperature water into said pump.
 6. The pool coverof claim 5 further including means for drawing warmer temperature waterfrom an upper region of said pool into said pump.
 7. The pool cover ofclaim 1 further including: a first sensor for determining a firsttemperature of said pool water; means for determining ambient heatconditions; a processor for controlling functioning of said pump basedon said first temperature of said pool water, said ambient heatconditions, and a target temperature for said pool water.
 8. The poolcover of claim 7 wherein said means for determining said ambient heatconditions is a temperature sensor for determining an ambient airtemperature.
 9. The pool cover of claim 7 wherein said means fordetermining said ambient heat conditions is an incident radiation sensorfor measuring incident solar radiation.
 10. The pool cover of claim 7further including a control interface for allowing a user to specifysaid target temperature for said temperature regulation of said poolwater.
 11. The pool cover of claim 10 wherein said control interfaceallows said user to set a first time period during which said pumpoperates for said temperature regulation of said pool water.
 12. Thepool cover of claim 11 wherein said control interface allows said userto set a second time period during which said pump operates for saidtemperature regulation of said pool water.